13C-CP-MAS-NMR studies of flavonoids. I. Solid-state conformation of quercetin, quercetin 5'-sulphonic acid and some simple polyphenols.
13C-CP-MAS-NMR spectra were measured in order to characterise the orientation of hydroxyl groups of quercetin, quercetin-5'-sulphonic acid and polyphenol-type compounds such as catechol, pyrogallol and gallic acid. The locked conformation of the OH group in the solid results in an increased shielding of carbon proxime to C-OH hydrogen. Carbon shieldings suggest that there is orientational disorder of three OH groups of pyrogallol and gallic acid and that two OH groups of catechol are not equivalent. In solid quercetin and quercetin-5'-sulphonic acid the C7-OH points towards C6-H and the C3'-OH hydrogen is near C2'-H.
Wawer
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Department of Physical Chemistry, Faculty of Pharmacy, Medical Academy, Warsaw, Poland.
Zielinska
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D002247:Carbon Isotopes; D005419:Flavonoids / Q000737:chemistry*; D008968:Molecular Conformation; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D010636:Phenols / Q000737:chemistry*; D011794:Quercetin / Q000737:chemistry*; D013451:Sulfonic Acids / Q000737:chemistry
D002247:Carbon Isotopes; D005419:Flavonoids; D010636:Phenols; D013451:Sulfonic Acids; D011794:Quercetin